1. Field of the Invention
This invention relates to a magnetic element, especially a magnetic element with two magnetic cores for increasing space for coiling.
2. Description of the Related Art
In prior art, wires of a magnetic element are usually coiled on one magnetic core of a plurality of magnetic cores, and the coiling body of the magnetic core is parallel to the soldering surface of the magnetic element. Therefore, the length of the coiling body is limited by the electrodes on the soldering surface, and the space for accommodating the coiling wires is also limited when coiling the wires on the coiling body of the magnetic element.
When wires of the magnetic element are operated with high currents and high inner resistance, the temperature of the magnetic core of the magnetic element also increases. FIG. 1 shows a relation between the magnetic permeability of the magnetic element and its temperature. According to FIG. 1, when the temperature of the magnetic core reaches the Curie temperature (ex., the Curie temperature of a high magnetically conductive material of Ni—Zn Ferrite may be about 110° C.), the magnetic core may nearly lose its magnetic permeability, namely, the magnetic permeability of the magnetic core may be as low as the magnetic permeability of air. Therefore, inductance of the magnetic element may decrease and the output signal of the magnetic element may be distorted significantly. Furthermore, when the temperature of the magnetic element goes too high, such as even higher than the Curie temperature, the outer insulation layer of the wires may be softened, causing the magnetic element to be short circuited or lacking of voltage endurance.
According to experimental results, to ensure the magnetic element can be operated normally under 70° C., wires with greater diameter can be used. For example, wires with diameter over 90 μm (about two times greater than the diameter of traditional wires) may be used to prevent the temperature of the magnetic core from reaching the Curie temperature. However, to generate the same inductance, the wires with greater diameter must require more space than wires with smaller diameter require for accommodating the same number of coils. Although the greater length of the magnetic core may increase the space for coiling, the footprint of the magnetic element may have to be changed accordingly, causing the issue of hardware incompatibility. Therefore, how to adopt the wires with greater diameter to prevent the wires and the magnetic core from reaching high temperature while preserving the inductance, the area and the footprint of the magnetic element has become an issue to be solved.